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What could cause an irregular climbing pattern on takeoff?
Yesterday (Dec 21, 2015), I was on board Ryanair flight FR4966 from London Stansted (STN) to Lamezia Terme (SUF). The aircraft was a Boeing 737-800, registration EI-EFW.
On takeoff, the climbing pattern didn’t seem very regular to me. It was clear that the engines were first running at full power, but then decreased their thrust and our altitude seemed not to increase as it would regularly do. I was certain we were about to return to STN due to some kind of malfunctioning. However, we reached our destination flawlessly.
Later, I checked the climbing pattern, and my impression was confirmed. You can see below that the climbing pattern was initially steep, but at an altitude of approximately 5,700 feet, the aircraft stopped climbing and proceeded at the same altitude for about 5 minutes.
My question: what caused this steady situation? Did the aircraft undergo a malfunctioning that the cabin crew was able to cope with? Or was it just due to the fact that we were overflying London — a congested airspace — and that was our assigned altitude?

The most likely reason for stopping a climb in congested airspace would be to avoid conflict with traffic. That happens quite often.

Related

"climb unrestricted" -- words to live by

The brief period of leveling off is not unique to the flight on that day. Looking at track logs for previous days, it always levels off at around 7,000 feet for some period.
As Terry commented, this is most likely to deal with the congested airspace. Other routes coming into and out of the London area probably pass through the same space, and keeping flights departing Stansted at a lower altitude prevents them from interfering with other traffic.
Looking at a standard departure chart, there is a warning box:

WARNING
Due to interaction with other routes, do not climb above 5000 until instructed by ATC.

This looks to be the route followed by this flight, at least to the DETLING VOR, so it would be expected that ATC will need to limit the flight's climb until clear of other traffic.

Looks like an intermediate altitude assignment from atc. A look at the standard instrument departure plates (SID's) for Stansted shows that the final altitude on some of the procedures is 6000 ft. They probably had to stay at that altitude until the departure controller passed them off to the en route controller who assigned them their cruise altitude.
On the initial IFR clearance, if I'm not mistaken, clearance delivery will give them a time to expect this assignment. The clearance will say something like "climb via [name of SID], expect flight level 350 one zero minutes after takeoff." My wording may be off. The departure controller will assign whatever altitude they need them to be at. Usually what's on the procedure. So they stay at that altitude until the en route controller assigns their cruise alt.

I picked a random SID plate for Stansted. At the bottom of the plate it tells what altitude they have to be at by a certain point. Looks like they have to get to 5000 ft pretty quickly.

In the USA, if the airspace is not too busy you can expect to get the next climb before you hit the previous limit and are forced to level off.  However, if things are busy, you may just have to level off, cruise, and wait for that next climb!  :-)


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What types of non-permanent GoPro mounts exist for the ceiling of a Cessna 172?
What alternatives are available to using a permanent mount to place a GoPro on the inside ceiling center of a Cessna 172?

Related

Many aviators use RAM mounts, which have all sorts of different mounts for different devices, and different attachpoints like suction cups, clamps, and screw-on attachments.

RAM mounts are awesome - if you aren't worried about damaging the aircraft, there are a lot of different clamp and screwdown options as abelenky said.

Thanks all.  I need something that's not permanent since the aircraft belongs to my flight school.  Ideally something that can provide a view from the middle of the two front seats forward.  I wish I could use the GoPro adhesives on the ceiling but unfortunately they don't come off easily...I'll look at RAM mounts.

I do tests on truck aerodynamics, and occasionally we put tufts on the vehicles. We then film these tufts to see how the flow behaves. We also use these RAM mounts, but sometimes one of them would come undone due to unproper mounting, dirt or flexing of the surface.
We solved this issue by adding redundancy in the form of the Rollei 3x Suction Cup Kit:

Disclaimer: Not affiliated to Rollei, this is just the first one we found.

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How do you make sonic booms quieter
I was looking through several sources and I can’t find anything explaining how sonic booms can be muted. In the Lockheed Martin Quesst experimental airplane info it states that it supposedly has a “whoomph” instead of a “boom” sound, which makes it quieter. Can someone explain how this actually happens? How do you change the sound and volume of the sonic boom? Here is an article about the project.

You use  the X-59 Quiet SuperSonic Technology?

The best ways to reduce sonic boom is to reduce the volume and mass of the aircraft.  After that, you can work on shaping the aircraft to change the characteristics of the boom.
The boom sound comes from a pressure wave passing over the observer after the aircraft flies overhead.
Although an aircraft is a complex shape that may have many shocks and expansions in its flow-field, far from the aircraft the initial shocks tend co coalesce into one strong shock, followed by a gradual expansion, followed by a final shock at the end of the aircraft.  This is called an N-wave.
This N-wave is the classical shape of a strong boom.  The characteristic of the noise (intensity and tone) are largely determined by how high the initial pressure peak is and how quickly it is achieved.
 Figure from this paper.
If we can reduce the initial peak and lengthen the pressure rise time, we can reduce the boom.  This usually requires working to prevent the shocks from coalescing together.

The volume: you reduce the area which cause the boom, so less air displaced per area and so less pressure (so volume). A small meteorite has less volume compared a larger one. i assume that engines and other less aerodynamic parts are more sensible to make louder boom. Note: the sound is difference on pressure, one may also do destructive waves (with some phase difference).
The sound: you create the boom at different times (e.g. in various parts of the wings, with some time difference, e.g. 1/5 second or longer).
How? It is tricky (and not a supersonic engineer). I assume that with new materials, we may get some slight design on aircraft surface, which has minimal aerodynamic effect, but which can reduce supersonic boom.

"How? It is tricky", some ideas in Review of Sonic Boom Prediction and Reduction Methods for Next Generation of Supersonic Aircraft. It's tricky.

The easiest way is by flying at the maximum altitude possible. This will dilute the shock energy over the largest possible area on the ground.

That can help but it still can be pretty loud for people directly under the flight path, like in this video taken on a ship as Concorde passed overhead. Supersonic aircraft could possibly follow routes that avoid direct overflights of major cities, but at some point a zig-zag pattern will become inefficient and there are going to be inevitable direct flyovers.

@StevePemberton, agree on all points. My personal feeling is nobody needs to travel at supersonic speeds in a passenger plane in the first place: no SST's means lots less sonic booms.

nielsnielsen - I think we will probably see Mach 1.2 business jets. From what I have read the methods being developed to reduce sonic boom levels only work up to about that speed. There is supposed to be a multi-month test creating booms of this level over a U.S. city to gauge public acceptance. Mach 1.2 is not fast enough to make the cost worthwhile for airline use, but is a decent speed improvement that probably many business travelers would be willing to pay for. For bragging rights if nothing else. I suspect many people flew Concorde just to brag about it not to save time.

@StevePemberton yes yes indeed, and there will always be people with enough money that the costs are immaterial. How do airplanes stay up in the air? Money, and the bernoulli effect. -NN

Although not enough people with money to support supersonic airline travel, as evidenced by Concorde. Of course it was limited because of overland speed restrictions as well as relatively short range, the only practical regular route being between east coast U.S. and western Europe (not counting charter flights). But even at its peak it only flew three scheduled flights per day each way across the Atlantic, which is about 600 passengers per day.  But business jets have a different business model, and especially with fractional use there are plenty of people with enough money to fly supersonic.

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Why do some fighter jets have two pilots while others have only one?
Why do some fighter jets have two pilots, while some have only one?
For example the newer fighter jets such as Dassault Rafale, Eurofighter typhoon etc. are mostly with single-seat, but two-seat models of these jets are also available.

Two-seat variant is needed at least for training. There don't seem to be two-seat variants of Typhoon or Rafale beyond that.

A lot of the time, like in the US Navy, if the airframe is a two seater one person is a designated Naval Aviator, and the other is an NFO (Naval Flight Officer).  The have completely different training pipelines and job specifications.  The NFO isn't a 'pilot' per-se, but has just as important of a job, if not more.  But, there usually aren't two pilots unless it's a training situation.

Consider some fighters has an attack variant (e.g. mirage 2000 D) which externally looks like the training variant but whose missions are quite different and require 1 pilot and 1 specialized crew member.

Speaking of fighters in their basic role, there are 2.
Interception and escort.
A single seat fighter would be superior in both scenarios because the space occupied by the second seater, plus the life support systems double the weight which can be put to fuel, countermeasures or weapons, and the extra weight and space will affect handling in air to air combat.
When the role is ground attack, 2 seat versions can be an advantage, such as SAM suppression mission, bombing and other types of strikes.
All of the above applies to modern aircraft.
Previously, say the 1970s and before, 2 seat fighters were sometimes necessary due to the technology available at that time. The F-4 and F-14 for example, the 2nd seater operated the radar because the pilot really couldn't keep his head in the cockpit when engaging multiple enemy contacts or when the fight was close in. Head up displays weren't available so the aircraft systems available to the pilot by necessity was kept limited in order to limit pilot overload.

Worth noting that HMCS wasn't available either, and it wasn't really until the addition of Multi-Function displays (IE: Glass Cockpit) that the workload could be balanced for a single person to manage in a cockpit. I wouldn't limit the answer to just 'because it's better for bombing to have two people', having two pairs of eyes on a hostile enemy aircraft is equally beneficial.

@Mark - True, but AWACS makes a lot of the RIO's traditional duties redundant in a CAP mission. Most two-seaters used in combat today are tasked with ground attack or electronic warfare; the pilot flies the plane, the GIB finds or blinds the targets. That doesn't mean they can't fight in the air as well (the F-15E has been used for Strike/CAP and HAVCAP sorties as its fuel load gives it extraordinary range and station time, while its missile ordnance doesn't compromise its ground stores capacity), but the systems and crews are more suited to attack missions.

All fighter aircraft have one pilot, though some have two crew members.
The backseat crew member is not a pilot, but often either a Radar Intercept Officer (US Navy), Navigator/Weapon Systems Officer (USAF, IDF), or Flight instructor.
Though not fighter aircraft, I believe that the SR-71 backseat crewmember operated the reconnaissance equipment as the single crewmember on the U2 was often overloaded with keeping the thing in the coffin corner and operating the reconnaissance equipment. Jan and Habu mention in the comments that the SR-71 backseat crew member was also the navigator and operated the ECM equipment. Additional comments mention that the B-1B consists of four crew members: two pilots, an OSO (offensive systems operator), and a DSO (defensive systems operator). The B2  has two crew members, both pilots, and while one is flying the other can rest, navigate, or operate the weapons system. Thanks to Jan, Habu, and Joel for comments and clarifications!

The second crewmember of SR-71 was also navigator. The navigation computer could have only be programmed from the rear seat.

In B-2, the crew members take turns at the controls so they can get some rest (36-40 hour missions are rather common; they have some place to lay down behind the seats), so both have to be pilots. The pilot not flying does the other tasks like navigation and weapon system operation. B-1B has 4 crew members, so 2 of them are pilots.

The second Blackbird crew member also operated the ECM suite. The guy who wrote Sled Driver joked that if they ever got shot down and captured, he was gonna point to his RSO and tell their captors that the RSO was the spy and he was just the driver.

@dotancohen: I mentioned B-2. They are both pilots. Only one is needed to fly the plane, but they take turns on long missions.

The B-1 has a crew of four.  Pilot, co-pilot, OSO (offensive systems operator) and DSO (defensive systems operator).
Generally any "backseat" crew member in a military aircraft will be generically referred to as a "wizzo" (for WSO).  Though their specific role varies by aircraft, their general purpose is to take avionics workload away from the pilot.

@Joel M - that's 99% accurate, but in non-combat military planes (USAF) (e.g. other than fighters and bombers), the "backseater" will be called a Nav or a Combat Systems Officer, not a Weapons System Officer

@dotancohen you wrote "All combat aircraft have one pilot,though some have two crew members." and then explain the B1, the B2 (and the B52) have two pilot, and the B1 (and B52) have more than two crew members.

@ManuH: I do see the confusion, so I've replaced 'combat aircraft' with 'fighter aircraft' which is not only more descriptive, it also fits the question asked better. Thanks.

@dotancohen I'm not quite sure we agree about definition of combat aircraft. For me, aircrafts whose mission is to deliver weapons on a combat theater is one type of combat aircraft (include bombers and fighters)

@ManuH: That is why the change to 'fighter aircraft' is more descriptive.

@habu: You username just 'clicked' for me! Were you involved with flight operations of the SR-71?

@dotancohen Haha, I wish. I was still in middle school at the time of the Blackbird's final retirement. I do have a massive nerd crush on both the A-12 and SR-71 though, hence the handle.

It's primarily a question of pilot workload and military policy at design time.
You'll notice that the primary two-seat fighters and attack planes in the U.S. armed forces (designation F or A) were designed in the late Korean through Vietnam eras, representing the third and early fourth generation of fighter design. This was a critical period of transition from the fighter philosophy of the World Wars and Korea, primarily day fighters engaging in visual-range combat with guns, to modern air combat involving all-weather precision engagements beginning BVR through use of radar, missiles and targeting computers.
As these systems were added to fighter cockpits in the early "century series", developing what would eventually be known as the "multirole fighter", pilot workload grew dramatically compared to the relatively simple layouts and weapons systems of propeller and early jet dogfighters. As a result, these systems, intended to increase pilot situational awareness, ended up doing the exact opposite, forcing the pilot to keep his head "in the cockpit" reading gauges and displays, with his situational awareness of what was going on outside the plane somewhere around his ankles.
With the problem identified but insufficient technology to take critical "heads-down" tasks like navigation away from the pilot, designers initially addressed it by adding a second crewman, whose job it would be to handle tasks not directly associated with the primary operation of the plane, such as navigation, managing the radar, keeping an extra pair of eyes on the sky around them, handling radio communications, etc. This guy is officially known in most situations as the Radar Intercept Officer or RIO, or informally as the GIB (Guy In Back).
It would take a few more technological developments, like the inertial navigation system, heads-up display, HOTAS control layouts, the integrated fire control computer, and advanced C4I capability like AWACS/JSTARS, before the workload inherent in the average fighter sortie could reasonably be handled by one crewman. AWACS can guide and advise pilots much like civilian ATC, the inertial navigation system allows pilots to simply point their plane in the indicated direction as opposed to monitoring nav beacons to figure out exactly where they were, and the HUD and HOTAS got the pilot's head out of the cockpit by placing the information and controls he needs to fly the jet effectively in combat where they're supposed to be; right in front of him and/or at his fingertips.
The primary fighter and attack jets of the third and fourth generation to utilize a 2-man crew include the F-4 Phantom, F-111 Aardvark, A-6 Intruder, the F-14 Tomcat, and the B and D variants of the F-15 Eagle, F-16 Falcon and F-18 Hornet. Notice by the development of the F-15 through F-18 that designers and US top brass were already considering single-seaters to be sufficient; the development and integration of the aforementioned systems into U.S. fourth-generation fighters had successfully made the workload presented by the plane more manageable by one person, thus the backseater (who required expensive flight training just like the pilot) could be moved to a second plane as pilot instead of riding along in the first, and the B/D variants of the Eagle, Falcon and Hornet were primarily used as trainers. However, all these designs were laid out in both one and two-seat variants just in case; the next fighters developed domestically for the USAF, the F-22 and F-23, were single-seat only (at least one two-seat F-22B was built, whether as a trainer or preproduction evaluation model, but the USAF never seriously considered a two-seater). The F-35 was never even proposed as a two-seater, primarily because every cubic inch of the design is spoken for especially in the STOVL-capable B variant.
The remaining two-seat fighters in the U.S. arsenal are the F-15E strike fighter (the backseater having the unique title of "Weapons Systems Officer" or "Wizzo" and being responsible for the fairly complex radar and targeting systems aboard) and variants of the F/A-18 including the F-variant "Super Hornet" and G-variant "Growler" EW fighter. In all these cases the GIB usually manages the advanced radar, targeting and jamming systems of these craft, as well as assisting in dogfighting by providing a second set of eyes especially behind the aircraft. The EA-6B Prowler, an older EW aircraft replaced just this year with the EA-18G Growler, had a crew of four; one pilot and three countermeasures officers.

In addition to Vivian jeet Singh Sudan's answer, most tactical aircraft also have training versions, which are indeed two-seaters with dual flight controls with the instructor sitting in the back.
The two-seat Eurofighters, Rafales, versions B & D of the Eagle and Fighting Falcon, anything from MiG or Sukhoi with a -UB suffix, etc. are all examples of this. That's not to say that they can't be operated in a pilot + weapons officer configuration (or single-pilot for that matter) and they normally retain full combat capability, but they're primarily intended for initial training, checkrides, and the like.

The F/A-18F Super Hornet is a two-seat variant intended for use as a strike fighter; it's basically the Navy's answer to the F-15E. These aren't just trainers (though the F is also used by TFA-109 in that capacity).

The Rafale-B is not a training version.

The primary reason any fighter aircraft would be designed for two crew members is work load.  As avionics, sensors and weapon systems advance they become easier for a single pilot to operate, which is why far fewer fighter aircraft have two crew members now than in the past.

Others have already provided many details on the uses for two-seat fighters, US names and practices, etc. but note that for the Rafale specifically, the two-seat variant is not merely a training version. In fact, some users, including the French Air Force, have more two-seat than single-seat planes.
The person seating in the second seat is often a “navigator” who assists the pilot and operates the weapon systems but I think that their controls are exactly the same so that the plane could be piloted from the back seat. Note that the Rafale was not designed as a fighter but as “multirole” aircraft, doing everything including reconnaissance, ground attack, close-air support, and nuclear strike.
Some missions benefit from a two-man crew while others do not, hence the two variants. On the other hand, the reason why some planes only have one seat is that the single-seat variant has a lower cost, lower weight and extra fuel tanks.

Two-pilot versions of almost all military planes exist (including the SR-71 until its retirement). They are for training pilots to fly them.

There's a couple that don't, like the A-10, F-22, and F-35. On those, your first flight in the aircraft is solo

There actually was one A-10B two-seat variant built as a possible trainer, but the USAF never bought any. Likewise, one F-22B two-seater was built for evaluation but that variant was scrapped as cost-cutting forced the USAF to prioritize the A variant. No two-seater of the F-35 was ever built.
As far as their use, it's not just for training; All variants of the F-14 (A-D), the F-15B/D/E, F-16B/D, and F-18B/D/F/G were procured by the U.S. with the intention of combat use; the backseater typically manages the radar and provides a second set of eyes.

Unless there has been a major change in AF doctrine, a two-seat fighter will ALWAYS be necessary, simply ask this question "When was the last time any ONE person could even be ALONE in a room (remember "NO-LONE ZONES" ) with a nuclear device, let alone having full control of one?"  The Air Force I served for 24 years would answer "NEVER!"  Even if a "mad" pilot could somehow steal a fighter with a "silver bullet" hanging on it, nothing would ever happen because with no warm body in the back seat to activate the "Nuclear Stores Consent" switch, the nuclear store goes nowhere.  The pilot could try and pickle off the bomb, but without toggling that switch in the back, the payload stays onboard.   The only AF fighters (that I knew about anyway) having this switch were the F-111, F-4, F-16 (two seat), and F-15E Strike Eagle.

This article indicates that the single-seat F-35 will carry nuclear weapons, so I guess AF doctrine doesn't work the way you remember it. (Or perhaps you mis-remember only B and D model Vipers being nuclear capable.)  In any event, the F-35's capability shoots down your theory.

See "Stranger to the Ground" for a counterexample.

With the technology available today, the ideal number is zero. But traditionally many tactical fighters had a crew of two because it made for more efficient operation in missions with a high workload. The "backseater" would perform tasks like interpretation of radar imagery, navigation and the operation of ECM (Electronic Countermeasures) while the pilot concentrated on flying.

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What are the factors behind increasing aircraft window sizes?
Modern airliners like the Airbus A380 and Boeing 787 have bigger windows than older designs, like the Boeing 737 and Airbus A320.
What factors have led to this change of window size, opposite to the trend of almost every other thing in the interior of the plane becoming smaller in size (like the seats).

Look at that difference in hull size.

It might have something to do with the frame dimensions. If it's farther from rib-to-rib within the body of the plane, there's room for a bigger window. I'd think that the A380 likely has a bigger frame size (front to back) than a 737. Here's a thread that has a lot of schematics, including frames, but, unfortunately, I don't seem to see actual frame dimensions.

Passenger windows or cockpit windows?

In the early years of the jet age, which followed closely on the introduction of pressurized hulls, there was much fear of stresses specifically in the area of the window openings due to the loss of two DeHavilland Comets. Subsequent Comet hulls had different shaped, rounded, smaller windows and that trend continued in other pressurized, typically jet-powered, aircraft.

Only with modern CAD systems and new materials knowledge could windows be made larger again. The newest aircraft designs reflect that progress.

up vote. Certainly engineering advancements is a key factor; but this particular accident in the very early days of high altitude pressurized flight was certainly a motivator for such engineering.

The Comets were lost in the mid-1950s; the A380 was designed in the early-2000s. You seem to be saying that very little progress was made during most of those ~45 years.

@DavidRicherby:  Quite the opposite. You don't need me to tell you that aeronautical engineers are conservative in dealing with safety issues on commercial aviation. The first fully computer-designed automobile, the LH-series Chryslers, were unveiled in 1992 or thereabouts. The fruits of those engineering efforts only came to commercial aviation in the models designed about or after that time period. As confidence built up in our ability to model the behaviours of metals and other materials under load, so did the size of the holes that we were confident to put in aeronautical structures grow.

Improvements in Engineering knowledge are an important factor.
Going from the time of the first 737 to the A380, there was a huge development in engineering techniques. Better material knowledge, more advanced modeling methods (such as more advanced Finite Element Methods, see this link for the history of FEM methods, thanks @Gürkan Çetin), and better knowledge of structural optimization have improved the situation. Especially with windows, where a lot is happening due to stress concentrations, this improved knowledge makes a difference.
This means that bigger windows might still lead to an increase in weight, but there will be a less severe weight penalty than the same windows using B737 age techniques.

It sounds strange to me that Finite Elements was not used in the design of the B737. Better materials knowledge, for sure, but FEM, I don't know. FEM got popular by 1950's at big corporations (like boeing), and Boeing 737 development had started in 1965.

Do you have any sources for this? I can imagine that some form of FEM might have used, but with the computing power of those days, it couldn't be very detailed. And if you're correct, the argument still holds for the giant leap in progress that has been made because of better methods, more computing power etc.

It was a surprise to me, so before commenting, I googled for FEM history and B737 history. B737 is from Boeing's site, and the other one is from a university paper: home.iitk.ac.in/~mohite/History_of_FEM.pdf . On the other hand, You're correct that, the advances in computational methods (mainly of algorithms side) and computational powers have advanced the way aircraft design processes are conducted.

It is the use of composite materials in the aircraft body structure that has enabled larger windows.
Metals are a crystalline structure that over time tend to fracture along crystal structure defects. Some key areas (e.g. turbine blades in the engine) are actually created by growing a single crystal to obtain higher failure points.  This is not possible over a structure the size of the aircraft frame.
When an aircraft is at altitude, it is like a pressurised balloon.  its skin is under tension, and when it on the ground, that tension is removed.  This is like constantly flexing a metal paper clip. The cross sectional area of the aircraft skin that carries this tension is reduced by windows - bigger windows put bigger strain on the airframe structure which tends to concentrate at corners.  making corners rounded helps to spread this stress.
The composite materials used in new planes are fibrous in structure. This greatly reduces the risks from the repeated flexing, allowing larger windows (and as the rust risk is reduced, cabin air is allowed to be more moist with also aids in flight comfort of passengers)

Let me answer with a car analogy: In most cases, the next car model is larger than the one before. Similarly, the aircraft manufacturers make the windows a little bigger with every new model, just to have another argument why the new model is better than all the competition. This costs a little weight, but seems to be worth it for the airlines.

Every next model is larger than the one before. This depends on the common trends of a particular period. Chevrolet Caprice, for example, is 18+ inches smaller than its predecessors. However, I agree that newer models are marketed as being better than the ones before, although there can be exceptions.

And the A319 is newer and smaller than the A320. The buyer is an airline, and they look first and foremost at the cost per passenger-mile. A bigger window isn't helping with that.

@MSalters: A derivative cannot have a different window size. And the car size increase within a model range doesn't mean the next compact model is larger than the sedan that came before it. Did you misunderstand me on purpose, or is my wording really so confusing?

@PeterKämpf I misunderstood in the same way so, yes, I think your wording is confusing.

As well as the advances in engineering, it is worth considering the comfort of the passengers. It is often thought that the more natural light in the cabin the better the experience for the passengers. More light increases the feeling of space, and can even reduce the fatigue experienced as a result of air travel. Whether or not there is much science in this I do not know.
Some Aircraft manufacturers use the window sizes as a big selling point. Gulfstream aircraft, for example, allow in more light than any comparable aircraft due to their oval shaped windows. In an attempt to compete Dassault are putting more windows on their newer Falcon 8x and Falcon 5x models.
Both companies have also introduced windows in the galleys in some models (Dassault famously with the 'sky light') as this is  typically the darkest and narrowest part of the cabin. In the cabin configurations most typical in Europe, the galley is at the very front of the cabin and is the first thing you see when you enter the aircraft. I think it is safe to say that it is much nicer to walk into a bright, airy space than a dark, narrow corridor.
Gulfstream 650 window details:

Sixteen large Gulfstream panoramic windows, each 28 by 20.5 inches/71
by 52 centimeters, allow abundant sunlight into the cabin, even in the
galley. Every window has been repositioned higher on the fuselage to
maximize viewing comfort*

http://www.gulfstream.com/aircraft/gulfstream-g650
Falcon 5X window & 'skylight' details:

Increased natural light does more than improve the view. It elevates
your mood and enlarges your perspective. The 28 large, expansive
windows of the 5X provide unbeatable luminosity.
The Falcon 5X offers an unprecedented direct view of the sky overhead
through its skylight ceiling window. This unique window on the sky
transforms your perception of space while providing natural light from
above.

http://www.dassaultfalcon.com/en/Aircraft/Models/5X/Pages/overview.aspx

One of the important things I'd like to add to the previous answers is that the old aircraft used to have smaller windows to accommodate for the rate of cabin depressurization in case of an emergency. The old airplanes had much smaller windows to control the cabin depressurization rate in case of some emergency (some window actually breaking to cause hull breach). But with advancement in the design methods and manufacturing process and with the introduction of the newer materials for airplane manufacturing, it has become possible to increase the size of the windows without increasing the risk factor.
In addition to this, creating an ambient atmosphere for the passengers inside the airplane without increasing the cost of the flight has always been a priority. So, while decreasing the seat spacing to accommodate more passengers is being done to reduce flight cost, the increase in the size of the windows does not have determinal effect on the travel cost, and hence is favored to create a less claustrophobic atmosphere inside the plane.


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What is the reason for different engine configurations seen on Solar Impulse?
In various images of the Solar Impulse aircraft, I see the engines mounted in different positions along the wing.  Am I looking at SI 1 vs SI 2, or are the mount positions capable of reconfiguration depending on conditions/experimentation?

Welcome to Aviation. Maybe you can provide URLs to two images showing the difference, that someone will convert in inline images.

Solar Impulse 1 had 2 engines right next to the fuselage, and the other 2 further out where the wing bends upwards.

Solar Impulse 2 has a pair of closely spaced engines on each wing, located partway out onto the wing.


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Climb angle relationship to excess thrust
In the PHAK, Chapter 5 Aerodynamics, the following statement is made regarding forces in a climb:

The thrust required for a stabilized climb equals drag plus a percentage of weight dependent on the angle of climb. For example, a 10° climb would require thrust to equal drag plus 17 percent of weight.

I believe this is derived using trigonometry, using the sine of the angle of climb. Is this correct? How would one visualize this using a right triangle? Thank you.

Highly related: https://aviation.stackexchange.com/a/56476/34686

Yes,
$\sin(\theta)=\frac{T-D}{W}$
Where $\theta$ is the flight path angle.
Start by drawing a free body diagram of the airplane.  You can draw an airplane, or just a point at the center of mass.
Draw the horizon through the point.
Draw an arrow depicting the velocity vector through the point.  Since we are interested in climb, you want the velocity vector to be 'above' the horizon.  The angle between the horizon and the velocity vector is $\theta$.
Draw the four principal forces, Thrust, Drag, Lift, and Weight.
Lift is perpendicular to velocity.
Drag is parallel to velocity, but pointing in the opposite direction.
Weight points down, perpendicular to the horizon.
Thrust is approximately aligned with the velocity vector.
Now you can start to look at triangles -- or to sum forces.
Your instinct is probably to draw a triangle with legs horizontal and vertical.  That will work, but it is a hassle.
Instead, draw your triangle with the legs parallel and perpendicular to velocity.  You'll see a $W\sin(\theta)$.  That will show you're on the right track.

Good answer. Just a few additional comments. The greek symbol theta is normally used in aerospace engineering for pitch attitude, not flight path angle, which is typically associated with the greek symbol gamma. Also, an assumption baked in to the equation is small angle-of-attack (e.g., less than about 10 degrees).

@AeroAndy Yes gamma is (probably most) frequently used for flight path angle, but it is also used for the ratio of specific heats, which comes into aircraft performance in the equation for the speed of sound.  So, I find that many references will use something other than gamma -- and sometimes that is theta.  It is my preference, but certainly not universal.  You are correct, the small alpha assumption is lumped into the 'Thrust is approximately aligned with the velocity vector'.

For large AOA, you might want to take T*cos(AOA) instead of T, so that both T and D are aligned with the velocity vector, otherwise (T - D) wouldn’t make sense as they are on different axis.


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How do manufacturers/kit providers determine Vne?
Vne defines the maximum indicated airspeed which should not be exceeded. And clearly, doing so would result in "bad things" happening like flutter, etc. Presumably manufacturers do some sort of design work to determine likely Vne but how do they test for that? Exceeding Vne would put the aircraft into a structural failure situation would it not?

$V_{ne}$ is typically set to about 90% of $V_D$, the maximum design dive speed.  This difference provides a safety margin.  Above $V_D$, damage may occur due to flutter or structural failure, or controllability considerations may make the aircraft unflyable.  The aircraft is not guaranteed to fall apart at $V_D$ due to additional structural and manufacturing margins.
During flight test, the aircraft is flown above $V_{ne}$, up to, or close to, $V_D$.  Appropriate safety precautions are taken, e.g. parachute.  Any failure below $V_D$ indicates a design or manufacturing issue that must be resolved prior to certification.
The limitation to flight below $V_{ne}$ (as opposed to $V_D$) during regular operations provides protection against airspeed measurement errors, pilot errors and some margin against structural degradation over the lifetime of the aircraft.

The generic answer is:

Design Cruising Speed (Vc) = 33 * Sqrt (wing loading)
Design Dive Speed (Vd) = 1.4 * Vc
Never Exceed Speed (Vne) = 0.9 * Vd

Then empiric testing (wind tunnel or test pilot) is done to test and expand those.
Actual formulas are in the F.A.R. FAR/JAR-23 and a reference page with this question answered is in this forum.
Military and advanced civil design does finite analysis based on the material properties in a computer simulation to calculate failure at stress points based on the materials used and predict flutter but that's beyond any simple answer and in industry is done by entire teams of individuals.

It is exactly as pericynthion says. VD is one of the so called design speeds defined at design time. Many of the structural/aeroelastic characteristics have to be demonstrated at speeds up to VD during flight test. However VD is for certification flight testing only. Normal operation is limited to VNE. However VNE is for light aircraft only. Larger aircraft have VMO instead.


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How much is the Boeing 787 Dreamliner affected by teething troubles now, one year after commencing commercial operations?
Boeing's Dreamliners have been hit several times by small bugs, like fires in the batteries or other engineering issues. Are such incidents frequent when new types are introduced, and how much has the situation improved one year later?

What does "hit several times" mean?

by "hit" what I mean is, several bugs appear in the aircraft, which prevent it from flying.. Generally, airlines dont disclose what this bug was..

@AbhinavAgarwal: Actually, airlines do disclose technical problems that occur when flying. You won't find it on their web (it's not good for publicity), but you can find them on the web of the relevant aviation safety board.

Recently related: In what circumstances could a 787 stay powered on continuously for 248 days?

You can get a rough idea by searching B788¹ on AvHerald.
Airlines do report technical problems² to their overseeing aviation safety board (in India it is, somewhat unusually, part of the civil aviation authority, DGCA; in most countries it is a separate agency, e.g. NTSB in USA). And those publish them.
Also for technical problems, aviation safety board of country of manufacture would be consulted, so NTSB should know about most technical problems of B787 and it should be possible to find them in their bulletins.
The Aviation Herald collects such reports from various sources. Only incidents that occur in flight get reported and only “interesting” subset of them, but if there were any serious problems with a type, they would come up.
Further if some problem requires mitigation steps to be taken, the civil aviation authorities publish airworthiness directives, that describe steps airlines must take (and under which conditions and until when) to be permitted to operate the aircraft. Since Boeing is based in USA, any airworthiness directive regarding it would most likely be first published by FAA and usually taken over by aviation authorities in other countries.
As far as I know, the batteries were the only serious issue of B787 that required immediate modification throughout the fleet. There are many small ones, like any aircraft, but there does not seem to be anything else that would be significantly more common or serious than on other types.

¹ AvHerald lists aircraft by their ICAO identifiers in the article titles (and full name in the text). The ICAO identifiers distinguish the series, so Boeing 787-8 gets B788.
² Those that affect safety. So non-working in-flight entertainment would not have to be reported, but a short-circuit in it should be.


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Who pays for the compliance with Airworthiness Directives (AD)?

Airworthiness Directives (ADs) are legally enforceable regulations issued by the FAA in accordance with 14 CFR part 39 to correct an unsafe condition in a product.

Hence when an AD is issued, owner must comply with the AD within the stated time period in order to remain airworthy. This compliance ,of course, come with some cost. Who pay for this cost of compliance? Owner of the plane? Manufacturer? Or they somehow share the cost?

possible duplicate of What is an Airworthiness Directive?

@NathanG: The OP asks for who pays" not for what is it.

It depends on the agreements between the operator/owner of the aircraft on one side and the manufacturer of the aircraft and its suppliers on the other side.
Often there will be some form of compensation involved if an AD is issued when that AD is addressing non-compliance with regulations / standard in effect when the aircraft was produced. Normally there is some time limited warranty covering the costs of ADs at least partially.

This article in Federal Register seems to support this mechanism (see Costs of compliance section).

The cost of complying with an AD falls on the owner/operator of the aircraft. Failing to comply with an AD renders the aircraft unairworthy. It also could incur FAA penalties, but more importantly, it could result in structural damage or failure, and in some cases ultimately cause a fatal accident.

And as mentioned in the linked question, using an unairworthy aircraft voids the insurance policy.

He did not as for the void insurance claim

voretaq7's comment below the selected answer: "Failing to comply with an AD has one other critical impact: It renders the aircraft unairworthy. Aside from the regulatory implications, most insurance companies void coverage". Actually it could void the policy.

The operator is responsible for complying with it. But wouldn't the expense be covered by some kind of warranty most of the time?

@JanHudec That depends on the problem, the manufacturer, and the aircraft. The FAA issued AD 2013-02-13 requiring inspection of the control cables on Piper PA28-family aircraft for corrosion. Many of the affected aircraft are over 30 years old - it would be unreasonable to expect Piper to pay for this inspection on an aircraft that hasn't been near the factory in decades. Conversely Boeing may offer some compensation for ADs on a 20-year-old 737.


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How do long-haul pilots cope with boredom?
Imagine you're in a large jet on a long route on a major airway -- say, for example, you're in a 747 going LHR-JFK at night. It's dark, you're over the Atlantic, and ATC has cleared you to just keep on heading along at FL330 (or equivalent) for another ~1500 nautical miles.
As it has throughout much of the flight, the autopilot is effectively flying the plane. There's nothing on the weather radar, no adverse meteorological effects expected, and ATC ensures that aircraft are well separated. In short, other than occasionally changing radio frequencies, there is very little for you to do.
Just a week ago, you were in the simulator, practicing spin recovery, instrumentation inop procedures, engine failures epsilon before V1, and all sorts of other fun things that required your attention. In your spare time, you're a private pilot and enjoy flying VFR at lower altitudes with the occasional bit of aerobatics mixed in, and practicing what to do in all sorts of rare eventualities at odd attitudes. In other words, you like flying planes. Now, your job is to check that the sophisticated flight computers are still flying this plane, and that ATC have done their job properly. They are, and they have. For the next few hours, you're going to be doing nothing but sitting in a chair watching blackness roll past. You can't even talk to the guy next to you about the weather -- there isn't any!
How do long-haul pilots cope with boredom on long, uneventful segments? Is my above scenario completely not plausible (aside from the lack of weather) -- is there always something meaningful to do during a 7+ hour long flight? I would expect that pilot boredom or distraction would be a safety-critical situation, yet I cannot imagine a situation that involves two humans sitting in chairs in a small room for a long period of time where they will not be bored or distracted at some point.
Do airline transport pilots ever "hope" for "something interesting" to happen?

Hi Landak, welcome to Aviation.SE. Why is there no one to talk to? Where did the pilot monitoring go to?

Good point -- I imagine that both the PF and PM would spend a lot of time chatting to each other about random stuff -- which means that there is a risk that they're not adequately flying the aircraft. Perhaps I'm also asking "outside of critical flight phases, is it okay (if not desirable) to take your eye off the ball"?

you have an autopilot that will alert you if anything abnormal arises. both visually and with audio alarms.

The sterile cockpit doctrine is essential for crucial flight phases such as take-off, landing and approach phase. During cruise, it's a bit more lax...

There is always turbulence in a flight.

See that button marked "Mode T" on the FMC menu?  Tetris.

long-haul pilots cure boredom by reading Aviation.Stackexchange

LHR-JFK isn't flown in the dark. West-bound flights happen during the day and east-bound flights are overnight. Also, in the middle of the Atlantic, there is no ATC.

From what I know, airline transport pilots do not get large chunks of free time on a typical long-haul flight which you described. They may get small intervals of free time (e.g. 10-20 minutes), but for sure, not hours. They do need to constantly monitor if the airplane is flying on the correct course, on the assigned altitude, remaining fuel amounts and several other tasks, even when auto-pilot is engaged.
So what do pilots do when they are not flying at all?
Primarily, it depends on company policies. Delta does not allow pilots to do anything not related to flying the airplane:

"You can't read a novel, but you could read a manual about procedures
  or about the airplane," ... "You can't read a newspaper. You can't use
  a laptop. That's strictly prohibited."

But generally speaking, pilots engage in causal chats between themselves and flight attendants (when they visit the cockpit)1.
When there are more than two pilots, one is generally allowed to get some rest. They can also browse through magazines or read some books or flight-related material, but mostly stay alert and available. Some will study for an upcoming proficiency or rating. One of the two pilots can go to the bathroom too. Getting locked out depends on pure luck.
So in a nutshell, there are several different activities/tasks pilots will engage into, each different for a particular flight.
This is a funny little anecdote I recently read, which fits this discussion very well:

Murphy's law grants you a heap of emergencies once you start feeling
  bored in the cockpit.

1: As a ordinary passenger, I don't visit the cockpit, but I have noticed a few times what the flight attendants do. When they have free time, they have many things to talk about between themselves. Sometimes, they engage in small talk with passengers. They check their schedule and flights for the remainder of the day. Although the duties of flight attendants and pilots are entirely different, there are a bunch of activities which require their attention, and they can pass the time without getting too bored.

So in short, they take breaks and have a pulsatile workflow -- which probably improves their ability to concentrate. Good to know!

When there are more than two pilots, one is generally allowed to get some rest. If by 'get some rest' you mean 'sleep,' that is location-dependent. It is strictly forbidden in the U.S. for anyone in the flight deck to sleep. See this answer for more information.

First, for most long-haul flights, the total flight time is beyond one crew's daily maximum allowance (which is usually 8 hours in any 24-hour period; a flight from Sydney to DFW can exceed 16 hours so two crews and additional compensatory rest periods for all crewmen are required during and after an ultra-long-haul). These flights carry two flight crews; one is flying the plane, the other is sleeping. While not on duty, the crewmen are expected to do anything but think about flying the plane; read, play games, sleep (definitely sleep) etc.
"Extended Range" variants of airliners used for nonstops in excess of a single crew's capabilities must, by FAA regs, have facilities for crew rest. Here's an article showing a few examples. While tucked out of the way by necessity, most are actually quite comfortable, often way better than first-class. Crews usually transition one pilot at a time to keep at least one person out of the way while people are getting into and out of the flight deck.
Second, with the autopilot engaged, regulations require only one pilot to be in control of the plane (called the "pilot flying"); the other one, the "pilot not flying", can read, use electronic devices, go to the lav, even power nap. This is called "in-seat rest" and is allowed by FAA/ICAO regs for short periods of time; there is a procedure to follow for a pilot to start and stop in-seat rest (basically making sure it's safe to do so and that the other pilot is awake, alert and knows the other pilot's entering a rest period) and there must be a certain overlap time where both pilots are not in in-seat rest.
Third, your more modern airliner flight decks can integrate music players into the pilots' headsets, "ducking" or muting the music when there is radio traffic. This is allowed even for the pilot flying; the only requirement is that the pilot be able to hear and understand ATC transmissions, but ATC will not be constantly talking to the flight crew (far from it; they have way too much work to do regarding all the other airplanes operating in their airspace). So, the pilot flying can hook up his iPhone and jam out in the headset while keeping watch on the plane. Such devices can only be used during the same periods of flight the passengers would be able to use theirs, and the same requirements of an "airplane mode" etc apply to the crew's devices.

Just out of curiosity, can you give an example of an airliner with audio input for personal electronic devices? Any examples of operators allowing their use?

It appears, actually, to be less an integrated system of the plane and more an adapter that inlines with the headset connection. Here's one example for GA-style headsets: http://www.marvgolden.com/mg-26a-amplified-cell-and-music-adapter.html. Here's an aviation headset with the audio input built in (no info on whether it has a ducking circuit;l I'd guess not): http://www.mypilotstore.com/MyPilotStore/sep/7364?

As far as their use on commercial airliners, because the FAA regs give the PIC the final say over whether a device will or will not interfere with his aircraft's systems (and therefore can or can't be used), the captain can allow himself to use his own device. I would bet most airlines wouldn't want the PR nightmare of widespread public knowledge that their pilots were listening to music while flying, so I'd imagine it's banned by most company policies, but a glance through Google's forum results indicate professional pilots skirt these policies fairly often...

@KeithS The pilot "giving himself permission to use it" only applies to the regulations regarding whether a portable electronic device will interfere with the avionics or other such important systems. They cannot give themselves permission to violate SOP (unless they deem it would be unsafe to not deviate from SOP, in which case they have much more latitude... but I think that would be a very hard argument to make for using your mp3 player. :) )

I've not heard of anyone using two full crews, maybe SF to India. But typically there will be a 3rd pilot and they take turns rotating in the crappy bunk.


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Which of these is true for a glider flying with constant angle of attack?
I'm trying to answer the following question, but I'm not sure of which one is correct.

A glider is gliding with constant angle of attack along its path. We can assume the hypothesis of small angles. Under these conditions, the following has to be fulfilled:
a) None of the other answers is correct.
b) $C_L=C_{Lopt}$
c) $\hat{D} =$ constant
d) $\alpha=\alpha_{max}$
e) V must remain constant

Note: D with hat means dimensionless drag.
I've been trying to discard some of them but I'm still doubting about if the correct answer is (a) or (e). Can you help me guess which one is the right one?

Can you discuss your reasoning on narrowing it down to (a) or (e)?

is this a homework problem? doesn’t really make sense and seems light on context.

I have discarded (d) because the fact that the angle is constant doesn't mean it has to be maximum. Also, I discarded (b) because the optimal lift coefficient is attained at a specific angle of attack, not at a constant given one. I also discarded (c) because the dimensionless drag depends on dimensionless speed and load factor, which do not need to be constant. So I have left, (e) and (a). I'm not sure if the fact of having a constant angle of attack makes a constant speed, and if this one's not correct, the only left is (a). And yes, this is a question from an old exam I am trying to solve.

This is not a very good question because it is not clear whether the path is linear, or as one answer suggested, whether a "phugoid"-like motion might possibly be involved.  If the former, the answer would have to be c and e.

Two things are important here:

It is about a glider, so no fuel is consumed, and the mass is constant over time.
The angle of attack is constant. This means also that the lift and drag coefficients are constant.

If the mass and the lift coefficient are constant, and we assume a constant load factor (implied by the gliding along its path description), the dynamic pressure is also constant, and the airspeed changes with the square root of air density. Gliding implies that the altitude decreases, so the indicated speed will be constant, but the true speed will decrease. Unfortunately, the condition e) is not precise enough to make this distinction. e) could be correct or not, depending on the definition of V.
I would suggest that also c) could be a correct answer: If the angle of attack and the mass are constant, so should be the drag coefficient. However, gliding down also implies that the Reynolds number changes because true speed decreases and temperature increases over the glide. Strictly speaking, this would also mean a very slowly changing drag coefficient.
Answers b) and d) are false and I agree with your reasoning.

Just a minor point, gliding does not have to imply a decrease of altitude, if you are gliding within a rising air mass (very common with gliders in fact ;-))

@Lnafziger: Only in wave lift would the air be calm enough for the angle of attack to stay constant, but, yes, this is possible. All other forms of updrafts would cause AoA variations, so I was assuming flight in calm air.

Thank you very much! Your answer made me see the approach better. I agree with you that (c) is the most correct one! @PeterKämpf

As this is a exam's question, assuming the glider glide long enough so that the renolds number increase may be incorrect. The question assumes small glide angle so the altitude variation may be negligeable (not to mention that the calm air hypothesis is not mention).

"mass is constant over time" not with a relief tube! I disagree with the statement that there are AOA changes in lift. Lift can be quite steady, and this is an idealized question anyway.

Constant angle of attack implies a constant CD and constant CL.
The fact that the aircraft is a glider implies a constant mass.
'along its path'  does not imply that the path angle is constant.
In a phugoid motion, the flight path angle is oscillating and so are the speed and the load factor, but the AoA is constant (by approximation).
We can assume the aircraft is in a phugoid motion with low amplitude and/or long period, so that the hypothesis of small angles is valid.
I suppose the dimensionless drag is constant during the phugoid motion even though both velocity and load factor are constantly changing. They cancel each other out. The fact the dimensionless drag coefficient CD is constant is also a hint here.
My  answer would be 'c'

Thank you very much. I asked my professor to verify the answer and it was exactly what you told me.


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Why do fighter aircraft manufacturers still focus on making their planes more dogfight-worthy?
In today's age, when dogfights are simply a relic from the past, why do manufacturers keep on increasing their aircraft maneuverability, in order to make them better dogfighters. It is more understandable if they were to make stealthier or more efficient fighters, but when the dogfight is extinct, why make planes even more agile and maneuverable?

The last time fighter designers thought dogfights were a relic of the past, Vietnam happened. It's understandable that they would wish to avoid repeating the unpleasant experience of redesigning hastily to try to patch up dogfighting ability on a plane supposedly too modern to need it.

On a side note, increased manueverability may well help aircraft dodge SAM's

"...dogfights are simply a relic from the past...", "...dogfight is extinct..." - please justify these remarks.

And what about the potential for remote-piloted dogfighters? No need to haul around all that mass of pilot, accommodation, support/survival equipment/supplies, on-board instrumentation etc., no human factors-imposed g-force limitations, no risk of pilot loss/capture. Or would a simulated cockpit just not give a pilot adequate situational awareness to remote dogfight his way to a successful kill as effectively as an on-board pilot?

Because it's what their customers want.

When all aircraft became stealthy, how will they fight anymore? In dogfight, I pressume.

I know I might be bringing up a dead question, but reading the answers, I noticed that none focused on the converse answer: although dogfighting ability is given special thought during new fighter design, much work has also been put into BVR type engagements. The F-22 and its whole AIM-120 and AESA specialized radar suite comes to mind most prominently, but even the F-14/15 have aspects that enable it specially for both high speed long range engagements and close up turning fights. Sure, the Russians focused on dogfighting more than us, but BVR really can be seen as the future, right?

That same thinking, "dogfighting is dead", got the USAF and USN in serious trouble in Vietnam. The U.S. Armed Forces were convinced that the next major war would be against the Soviet Union directly, in theaters including Europe, Alaska and Canada, and as a result, fighter designs succeeding the very successful Sabre and Super Sabre day fighters used in Korea began emphasizing standoff capabilities, believing the aerial threat would come from various classes of nuclear bomber, calling for fast, long-range missile-armed interceptors as a counter.
That war, thankfully, never materialized. Instead, the U.S. was pulled into more or less another Korea, a proxy war fought between Soviet-supplied and trained Communist forces against a U.S.-backed fledgling democracy. The big, heavy U.S. F-4 Phantom interceptor and F-105 Thunderchief light bomber, neither of which had internal guns, found themselves facing the older like-minded successor to the MiG-15s they faced in Korea, the MiG-17, coupled with the MiG-21 close-range interceptor. Instead of the long-range standoff air war the USAF was built for, US pilots were ambushed at close range by guns and infrared missiles, resulting in a piss-poor 2:1 kill/death ratio in aerial engagements, compared to the 14:1 ratio they enjoyed in Korea.
The result was increased attention paid to "air combat maneuvering", and an emphasis on this style of combat in the next generation of fighters adopted by the U.S. military. The F-14 and F-15, though intended to bring back dogfighting (and they did), turned out to be big, fast interceptor-style fighters like their predecessors, that still only had a clear advantage in BVR engagements. So a group of USAF generals, seeing what its allies had been doing with the F-5 Tiger that the Joint Chiefs had more or less passed on (a few trainers, a few aggressor planes, but no combat adoption), commissioned the LWF competition, which would produce the F-16 and F-18 lightweight multirole fighters with an emphasis on the close-quarters maneuverability that the Communist powers never really forgot.
The F-22 splits the difference between the F-15 and F-16's air combat strategies, producing a heavier but highly maneuverable fighter that excels at air combat at any range (but is so expensive that so far the USAF have only deployed them in situations where they would never face any real threat). The F-35, however, is rapidly becoming a disappointment; compared even to the F-16 or F-15E it will replace, it "can't climb, can't turn, and can't run", and the A variant is the only one with an internal cannon (which carries only 182 rounds of ammunition compared to the F-22s 480, the F-15's 650 and the F-16's 510); the STOVL B variant and the Navy's C variant won't have guns at all.
In today's military theater, the U.S. enjoys "air supremacy"; we're fighting largely paramilitary forces with practically zero air to air capability. Tomorrow's theater, however, may be quite different. Diplomatic relationships with a number of Russian-supplied nations including Russia itself are souring day by day, and the U.S. could easily find itself drawn into conflicts over Taiwan, the Korean peninsula, India/Pakistan, the Ukraine, etc, where they'd face militaries fielding Russian jets purpose-built to mix it up at visual range.
In short, while the U.S. hasn't directly fought a conflict against a serious air threat since Vietnam, there are a lot of potential near-future conflicts in which they would get their chance, facing the Sukhoi PAK-FA or Chengdu J-20 with skilled Chinese or Russian pilots at the stick. Even if these fighters aren't fielded in mass numbers, the U.S. would still face the Russians' direct answers to U.S 4th and 4.5-generation fighters, including the MiG-29 and Su-27/30/33.  Many variants of these were specifically designed to out-maneuver the U.S. F-15, F-16 and F-18 (which would likely be the first jets in-theater), and which would still be a match for the F-22 in a visual-range "furball".

I don't know that your last statement is true - I've talked to some US Fighter pilots who have been in dogfights with the F-22, and even in their 4th-generation fighters they have little chance against the 22, with guns or missiles. They're good 4th-gen fighters, just not near the level of the 22

Those are U.S. pilots flying U.S. planes; the 22 was the first U.S. production fighter with vectored thrust. Try an F-22 against a Su-30MKI; the 30's radar cross-section is higher, but it has multi-aspect vectored thrust allowing high-yaw in addition to high-pitch maneuvers giving it a few extra tricks in a furball. I wouldn't count out the Su-30 in a one-on-one visual-range engagement.

Here's an article about the latest "Dissimilar Air Combat Training" exercises, Cope Taufan 2014, in which U.S. Raptor, Eagle and Hornet pilots went up against Malaysia's Russian-supplied air force of MiG-29Ns and Su-30s. The Su-30MKM, very similar but with different avionics than the Indian MKI variant, is a serious dogfighter that is not to be underestimated. Other exercises have pitted it against German Eurofighters. http://foxtrotalpha.jalopnik.com/us-air-forces-f-22s-f-15s-just-battled-one-of-their-m-1596305711

The consensus so far, which is limited because so much about the Raptor is heavily classified, is that the plane's best weapon is its stealth; it enjoys a significantly higher kill-death ratio in BVR engagements. Close the distance, and it can still mix it up, but a highly maneuverable 4th or 4.5-gen fighter has a chance, especially once the Raptor goes post-stall (using its vectored thrust to get the nose to come around). Once that happens the Raptor loses a lot of maneuvering energy, allowing a more energetic opponent to take the fight vertical and get some chances at an off-boresight lock.

I don't mean to nitpick; much of the aviation-specific information here seems relatively well-researched. However, where the answer veers into analyzing potential conflicts, it seems very speculative and factually inaccurate. Please provide some substantiation/source for the claims that (1) the UN and/or NATO recognizes Taiwan as a sovereign nation or (b) that NATO (or even the US for that matter) would have any obligation to respond in the event of Chinese aggression? The currently in-force Taiwan Relations Act does not set out any such obligation and is intentionally vague on this point.

By your own admission, much of the capabilities of the F-22 and F-35 are classified, and thus, any comment you've made about their tactical capabilities is either going to be pure conjecture, or a leak of classified information.  My money is on the former, making much of what you've stated your opinion, and probably not accurate enough to be included in your answer.

Something else worth considering is the political aspects of war - in some cases the ROE might not allow for BVR attacks. There's a good reason the AIM54 Pheonix was almost never fired in anger. There's no point in being able to detect an enemy at range, and hit them, if your ROE insists on visual confirmation.

@SSumner yes, 1-1 an F-22 will beat the living daylights out of an F-15 or MiG-29, but it won't be 1-1. Each F-22 will be up against possibly dozens of MiG-29s or similar adversaries, and they won't survive that (and depending heavily on AWACS as the F-22 does, when fielded in a warzone away from CONUS or the European theater it will be at an even greater disadvantage). And the F-35 is even worse, it can't even go up 1-1 with an F-16 and have a working chance of making it out alive, and that's the aircraft it's to replace (and at a 1-3 ratio or worse).

@jwenting - Actually, if allowed to fight the way it was designed, an F-22 is more than a match for 8 or more U.S. 4th-gen fighters. The first clue they're likely to get as to the F-22's location is a missile launch. Also, the F-22 would never be fielded alone in an environment with that many hostile aircraft flying; it's just too valuable. If we had to fight planes with planes, we'd supplement the F-22 in BARCAP with 15s, 16s and 18s, all of which are still perfectly capable of dogfighting all but the very most advanced jets in the Russian arsenal, most of which are in allied militaries.

More seriously, if we were going against a country with significant air power, airstrikes using cruise missiles targeting air bases would likely be the first move by the U.S.. Park a couple Arleigh Burkes or Ticonderogas a hundred miles offshore and let fly, likely followed by deep strikes with manned aircraft like F-15Es or B-1s to mop up targets that survived the missile salvo. The planes can't be in the air all the time, so if you destroy the runways and support infrastructure, the planes become useless.

@KeithS nice theory, but the practice of warfare is that things never go "as designed". The AWACS won't be there or jammed, the cruise missile strikes fail, etc. etc.

Why is everyone always talking about 5th-gen vs 4th-gen only? What about 5th-gen vs 5th-gen? A 5th-gen fighter is not able to detect another 5th-gen fighter, so that will probably lead into a dogfight, right?

Dogfighting isn't dead.  Even though generation 4.5/5 airframes have great missile capability and stealth, there are times when there is no substitute for bullets.  Close quarter gun fire is pretty much immune to chaff and flares.  Being able to maneuver into position to engage another aircraft with guns is essential in many circumstances and training for that will likely be a fundamental part of flight training for a long time, so, I doubt that manufacturers will stop developing more maneuverable jets even though electronic/computer systems are playing a larger part in air to air combat.

Being able to maneuver into position to engage another aircraft with guns is essential in many circumstances -- As is being able to maneuver into position to launch that expensive missile at your target. All the fancy missiles in the world do no good if you can't maneuver your aircraft into a position where you can successfully fire them at the hostile aircraft. That needs a very similar set of characteristics to those that make a good dogfighting aircraft.

Just an aside, dogfights aren't limited to guns.  Missiles play an important part in the modern dogfight as well.

@RhinoDriver - That's true, however modern short-range missiles can be fired "off-boresight", with the pilot simply looking at his target to cue the missile's seeker head instead of having to point the entire plane in the right direction. The AA-11 and the cutting-edge short-range IR missiles of virtually all NATO countries and allies are capable of at least 90* off-boresight targeting (the opponent being directly to the side or above), and the MICA IR, a French missile marketed to operators of the Dassault Rafale, recorded the first ever missile kill of an aircraft behind the launcher.

@KeithS My only point is that close range engagements are not limited to guns.  I'm not sure what your comment is suggesting other than dogfighting engagements are more complex now than they used to be 20-30 years ago.

ALL weapons have an acceptable launch envelope, and an unacceptable one, The only difference between guns and missiles is that missiles launch envelopes are generally larger than that of the gun. But the pilot still has to maneuver the launch platform (the aircraft he is flying) into the envelope for the weapon he/she is employing.

While dogfighting may be extinct in Afghanistan, its certainly not extinct in Russia, China, Europe, India, etc.  Nations do not arm to fight the current threat, they arm to discourage possible future threats and project power abroad.

And deciding that you don't need to be able to dogfight any more puts you at an instant disadvantage against anyone who can still do it.

@DavidRicherby exactly my point, you train to discourage future threats whilst simultaneously projecting power of your own.

@DavidRicherby OTOH, you don't bring a knife to a gunfight. Replace digfight with swordfight to see how that logic doesn't really work. Deciding that you don't need to be able to swordfight anymore puts you at an instant disadvantage against anyone who can still do it; not if the enemy is using machines guns and powered battle-armor. There is a reason we don't train with blades anymore. IOW, The reason people say we don't need dogfighting anymore is that we have capabilities to prevent the enemy from using their dogfighting ability. So the "anyone who can still do it" is no one.

@Shane Did you read the accepted answer? "We can prevent the enemy using any dogfighting ability they may have" was exactly what the US thought going into Vietnam and it was dead wrong. As soon as you lose the ability to dogfight because you think you can avoid getting into dogfights, any enemy who can get into a dogfight with you has a big advantage. Just as somebody with a knife has a big advantage against somebody with a rifle, if they can get within grappling range.

Some good answers here, in complement to which I would like to submit a very interesting paper (alternate link - pdf!) I came across on the promise vs. reality of BVR combat, which has been predicted to replace dogfighting since the 50s, if not 40s.
In short, history has shown that despite all advances, battlefield realities have consistently forced aircraft into close-range situations where traditional ACM capability still matters, so manufacturers have to take that into account if they hope to sell their aircraft. The only reason dogfighting is extinct in Afghanistan is because insurgents there have no aircraft of their own to operate. Operations elsewhere have demonstrated the continued relevance of having a platform that can maneuver when it has to.
There is, however, a reverse side to the coin in that, while maneuverability and thrust-to-weight ratios remain important, we may be hitting a plateau in terms of how much more that capability is being improved. So-called "supermaneuverability" is becoming a fairly ubiquitous feature in most modern dedicated air superiority fighters (e.g. F-22, T-50, Super Flanker series, the Eurofighter Typhoon in its air superiority configuration, etc.) but the levels of agility currently on display have often been first showcased more than 20 years ago.
In the meantime, other features such as stealth, supercruise, passive and low-probability-of-intercept sensor suites, data links, helmet-mounted sights and off-boresight launch capability for missiles, along with a massive push towards improving pilots' situational awareness have seen tremendous advances in the past 20 years and, to my mind, say a good deal about what the air forces of the world (i.e. the customers) perceive to be the elements that will give them an edge.
In short, dogfighting capability is still regarded as an essential capability, but only time will tell if its importance will diminish relative to other elements.

The levels of agility might still be improved by getting rid of the pilot; an unmanned aircraft isn't restricted to G forces that a human can survive. But of course that opens up a lot of other very difficult issues, like how to effectively control - in all senses of that word - an aircraft that can move and react faster than a human can. Self-driving cars are already bringing up some tricky ethical questions and autonomous armed vehicles will bring even more.

@Pondlife - agreed; I'm a huge fan of the idea of massed swarms of very cheap robotic UAVs whose sole job is to go out and drown the other side in targets, but I figured that might have been a little outside of the immediate scope of the discussion.

It's not close range per se. It's that your enemy is a human being. And being human they tend to be creative. When the Japanese had better maneuverability American pilots developed tactics that took advantage of their higher top speed. When Americans developed good missiles the Vietnamese took advantage of the minimum arming distance and closed in for dogfights. You simply can't afford to neglect any area of performance in case your enemies can exploit your shortsightedness.

The manufacturers aren't trying to increase their aircrafts maneuverability. The F-35 is far less maneuverable than the fighters it is replacing. Modern selling points include stealth, multi-role, reconfigurability, avionics, price, and data. It is all about Situational Awareness.
General Hostage of USAF says:

People focus on stealth as the determining factor or delineator of the
fifth generation. It isn’t; it’s fusion. Fusion is what makes that
platform so fundamentally different than anything else.

Lieutenant Colonel Berke says:

But the difference between a Hornet or a
Viper and the Raptor isn’t just the way you turn or which way you move
the jet or what is the best 43 way to attack a particular problem.
The difference is in how you think. You work in a totally different way to garner situational awareness and make decisions; it’s all different in
the F-22. With the F-22, as will be the case with the F-35, you’re
operating at a level where you perform several functions of classic
air battle management. That’s a whole different experience that
requires a different kind of training.

And from another pilot:

The whole point to fifth generation is the synergy of stealth, fusion
and complete situational awareness," says a veteran Air Force fighter
pilot. The point about fifth generation aircraft is that they can do
their mission anywhere - even in sophisticated integrated air defense
[IADS] environments. If you fly into heavy IADS with a great radar and
sensor fusion, but no stealth, you will have complete situational
awareness of the guy that kills you.

Maneuverability and dogfighting isn't a selling point. In fact lt.col Berke specifically dismisses it.

Moreover, the answer from KeithS seems quite off. The F-105 Thunderchief was a ground attack fighter-bomber.

As a follow-on to the Mach 1 capable North American F-100 Super Sabre, the F-105 was also armed with missiles and a cannon; however, its design was tailored to high-speed low-altitude penetration carrying a single nuclear weapon internally. [...] During the war, the single-seat F-105D was the primary aircraft delivering the heavy bomb loads against the various military targets. Meanwhile, the two-seat F-105F and F-105G Wild Weasel variants became the first dedicated Suppression of Enemy Air Defenses (SEAD) platforms, fighting against the Soviet-built S-75 Dvina (NATO reporting name: SA-2 Guideline) surface-to-air missiles.

Of course it isn't going to be a great dogfighter. Still, it rackered up nearly 30 MiG kills. The F-4 however was an Interceptor with standoff weaponry,

[its] biggest weakness, as it was initially designed, was its lack of an internal cannon. For a brief period, doctrine held that turning combat would be impossible at supersonic speeds and little effort was made to teach pilots air combat maneuvering. In reality, engagements quickly became subsonic, as pilots would slow down in an effort to get behind their adversaries. Furthermore, the relatively new heat-seeking and radar-guided missiles at the time were frequently reported as unreliable and pilots had to use multiple shots (also known as ripple-firing), just to hit one enemy fighter. To compound the problem, rules of engagement in Vietnam precluded long-range missile attacks in most instances, as visual identification was normally required. Many pilots found themselves on the tail of an enemy aircraft but too close to fire short-range Falcons or Sidewinders.

So while it wasn't designed as a dogfighter, that isn't the cause of its low kill:death ratio. Politics and 60s-70s era technology was.

This is much more on the money. But I'd disagree with the second sentence. Virtually every pilot testimony attests that the F-35 is quite maneuverable, with the acceleration of the F-16 and the high-alpha/low-speed performance of the F-18---basically a thrustier Hornet.

Haven't you seen Independence Day?
It's always better to be prepared for a category of threat than to write it off. Why teach a soldier hand-to-hand fighting when he has an assault rifle? Because you don't want to lose a perfectly good soldier when he gets surprise-jumped and doesn't have the time or space to bring his rifle to bear.
Additionally, the recent Defense spending trend in the U.S. is very large, very expensive orders of a particular vehicle. Those numbers are much easier to sell when that vehicle can (on paper) fulfill multiple roles. Just like in business, you're going to have some marketing wizard who's only job is to secure the biggest budget possible for your pet project, and his goal is to have an endless bullet-list of features to attract those dollars.

Your point is valid... but Independence Day? Which part are you referring to?

@fooot Presumably the part where Will Smith outmaneuvers an advanced alien fighter in a dogfight. After all, as a more recent movie tells us, no matter how advanced the alien civilizations, their aircraft can't bank worth a damn.

To be fair, alien ships are probably designed to work in the vacuums of space.  The extra air resistance is killer.  :-)

@ChrisKaminski. they must be primitives not to consider other planet's atmospheres!

From what I have read, and from the answers I have seen above, it looks like most of air combat will consist of BVR missile attacks, however, since nothing is 100% perfect, some of fighters will get through the initial missile salvo and end up in close - range air combat.
Why do manufacturers focus on "making their planes more dogfight-worthy?"
Answer: Just in case
This document may be useful:
http://www.dtic.mil/dtic/tr/fulltext/u2/a192214.pdf

authors: Bob Jarvis - Слава Україні


text:
Why don't most fighters have thrust reversers?
With the exception of the Panavia Tornado, fighters do not have thrust reversers. Why is this? Why does the Panavia Tornado have them?

The https://de.wikipedia.org/wiki/Saab_37 Viggen also uses thrust reversers.

Thrust reversal is a complex system (equals money) and it uses significant amount of fuel (also equals money). It is not a very efficient means to reduce the speed of a landing aircraft either, and other methods (e.g. brakes or drogue parachutes) are much better suited.
The biggest advantage of thrust reversal is that it cancels out the idle forward thrust working against the aircraft. Canceling out idle thrust isn't an issue on most fighters, as they have an engine nozzle that is open at ground idle to prevent any thrust from being produced. This nozzle probably also makes it a bit difficult to integrate Thrust reversals, but the Panavia Tornado proves it can be done.

... saving fuel on reverse thrust but always taking off with full afterburner... I don't think so

@Jan Rather than alluding what you think and downvoting, it is appreciated if you can provide some evidence.

I can only speak for the civilian sector where a friend of mine who flies large commercial aircraft told me that their company instructed them to be light on the brakes and rather use full reverse thrust. You can always refuel but changing the brakes costs time during the turn around and thus a lot of money. Given the mission profile of military jet fighters - takeoff as quickly as possible, have air superiority at the target region by being as light as possible and having a higher thrust/weight ratio than the enemy - being economical is not top priority.

In short the answer should be: Thrust reversal is a complex system which adds unnecessary weight which reduces the effectiveness of the fighter. Leaving it away reduces the turn radius and improves handling qualities of the fighter.

It of course comes at the cost of having to change the brakes more often but better repair an aircraft after the fight than not having an aircraft after a fight.

It has nothing to do with cost or wasting fuel.
A military jet is notoriously designed to do the best it can, to hell with how much it costs.
If expense of construction was a concern, they'd think it was ridiculous to build from exotic components just to shave a few pounds.
Fuel efficiency and fuel cost is only a concern in terms of being economical as possible in order to have the best range to attack the enemy, or to loiter on station on patrol. Wasting a little fuel on landing is inconsequential; why else would jet fighters have fuel dumps? It's common to jettison any few thousand extra pounds of fuel to get landing weight down, and it's also common to take extra fuel on from the tanker just in case. So you take three times as much fuel as you need to get back to base, then when you get there safely, you just dump it so you're light enough to land.
They don't include reversers because the extra weight and space they need would be better used for something else like fuel or avionics.
Military jets, especially fighters, are ridiculously expensive to operate, not just buy. Commercial aircraft, on the other hand, need to do things cheaply, with little maintenance and short turn-around times. Passenger aircraft and airlifters are far larger and heavier than fighters; that's why they need reverse thrust. A big enough parachute is a real pain to pack back up again, and replacing worn out brakes is expensive. A thrust reverser is extra initial expense, but it pays for itself.
Military large airlifters use thrust reversers to quickly unload and return for more, and to land on short runways; that's rarely a concern for a fighter. They may also need to turn themselves around for takeoff; while a fighter could be pushed by hand in a pinch, a C-5 Galaxy, not so easy. It's not surprising, in the few fighters that have a reverser (the Tornado and the Saab Viggen), landing on short or icy runways was a primary motivation, coupled with rapid turnaround, and the fact that parachutes are only effective at high speeds.

Welcome to Aviation.SE Kel!  If you could do us a favor and break down your one giant paragraph into smaller ones...  It's a little hard to follow as it's currently structured.

I agree with this answer. Fuel is dirt-cheap compared to everything else about a fighter, including operating costs. The reason is weight and space. Fighters need to be as light as possible for the sake of maneuvering. They also prefer to be a small target. Yes, the answer should be broken up into smaller paragraphs. But I upvote because I agree with pretty much every sentence.

Fighter aircraft are specialized tools optimized for a specific purpose: to destroy enemy forces (in the air and on the ground).  Everything that is not vital to that mission is quite literally dead weight that reduces the performance of the aircraft as it relates to its specific purpose.  Jet fighters are not required to "taxi back" on the tarmac, and simpler "speed brakes" are more effective at slowing down in flight.

Fighter aircraft are specialized tools optimized for a specific purpose: to destroy enemy forces in the air and on the ground the latter I would call them bombers, though, not fighters.

@Federico:  I think you will agree that many fighter aircraft have ground attack capabilities.

that's the "fighter-bomber" mashup (of which the Panavia is a member). if we want ot be purists, no, fighters are not made to attack ground targets, if we include fighter-bombers then, instead, yes I agree with you.

@federico Who said anything about being a purist?  The A-10 drops bombs, strafes, and blasts the insides* out of tanks with its GAU-8 gun.  I asterisked "insides" in a fit of political correcness....  Is it a fighter bomber?  No, its role is diverse enough that "fighter-bomber" doesn't really describe it well.

@SkipMiller you will convene then that fighter does neither.

@TUMBLEWEED I do not know the Viperjet, but from a quick search is not even a military aircraft http://en.wikipedia.org/wiki/Viper_Aircraft_ViperJet

@Federico: In the contemporary world, how many 'fighter' missions are flown against enemy aircraft?  FTM, do ISIS, the Taliban, al Qaeda, &c even HAVE aircraft?

@TUMBLEWEED what the general public calls a "fighter bomber" and often a "fighter" is technically called a "multirole fighter aircraft". The F-16 is one such, so yes it's a fighter-bomber (which is an outdated term, but still in common use). While designed as a light air superiority fighter the F-16 quickly evolved into a multi-role aircraft with extensive ground attack capabilities, which is the primary role it performs for most operators.

As long as we're splitting hairs about role designation, the correct terminology is actually attack or strike.  For example the F/A-18 is a fighter attack aircraft, and is also called a strike fighter.  Just like the air force has the F15E strike eagle.  In summation, everyone is wrong, and we're all retarded for even caring.

@skipmiller i am a bit lost. A-10 is attack aircraft with close air support(CAS) role. Idgi what it has to do with bomber or fighter.

The tri-service aircraft designation system, first off, is 53 years old this year; air combat has changed quite a bit in that time. Second, the "attack" specialization is primarily a Navy phenomenon; the USAF pretty much had only two classes, "Pursuit" (later "Fighter") and "Bomber". If it was capable of engaging another aircraft in a turning fight, it got a P or F designation, no matter what else it was used for (for example, the P-51 which did everything from bomber escort to tank plinking and CAS). This tradition continues today, with only one notable USAF "Attack" craft (the A-10).

The Navy as stated was the side that introduced the attack specialization into the light-craft spectrum, having used it for a number of dedicated ground-attack aircraft starting with the venerable A-1 Skyrader and continuing through with its current "multirole fighter", the F/A-18 (which performs a similar role for the Navy as the F-16 does for the Air Force). The next airframe the Navy will put in operation is the F-35C, and there's no indication that the Navy will continue the "F/A" designation, so the "Attack" moniker may well die when the A-10 and F/A-18 are retired.

The old Saab Viggen fighter also has thrust reversers. This was part of what made it so capable on short or improvised runways.
Wasn't useful enough to keep in the Gripen that replaced it, that is a much more conventional 4.5 generation fighter.

It is because they already have several ways of braking, so they don't need reverse exhaust.link This should explain to you the braking systems used by the f-16 instead of reverse exhaust. This jet you are describing may not have as many braking systems as a normal jet does so it uses reverse exhaust.


text:
How do most fighters slow down after landing?
I understand that many fighters use drogue parachutes and wheel brakes. But aren't there other methods of slowing down after touchdown?

Arresting gear on aircraft carriers?

I meant on runways on land.

Arresting gear is sometimes used on short runways for fighter / jet training  aircraft.

What about spoilers?

The primary purpose of spoilers is to dump lift so that there is more weight on the wheels and therefore better braking.  Speed brakes might be used.

Arresting gear is used only in emergencies for non-carrier qualified aircraft as it places severe stresses on the aircraft and is likely to cause damage. Think of situations where an overpeed landing is required and the aircraft brakes can't stop the aircraft in time.

@jwenting The spelling in your comment is amusing and perhaps appropriate for some of the types of situations you describe. :)

Another way to slow fighter jets down, is by using airbrakes.
These are basically two big flaps (usually located at the end of the aircraft) that extend into the flow. I think the airbrakes do most of the braking in the approach phase (as it is a good way to dissipate kinetic energy fast), but i'm pretty sure they're also used to slow down during the roll out.
Here's an image showing an F-16 landing with the airbrakes extended, the two protruding flaps at the end are the airbrakes.

As a bonus, here's a picture of one of the first airbrakes in the book Popular Science (1932):


text:
Why do most A320s make that distinct scream on takeoff?
I've noticed that the engines on the A320 make a very a distinct sound on takeoff. Is there something about the CFM-56 series that causes this?
This noise can be heard in this video.

If it were the CFM56, the 737 would do the same thing. A320's can also use IAE engines. Is there a video of what you are talking about?

https://www.youtube.com/watch?v=2m9l-nDd1fw

That's an IAE V2500 engine.

What is it that causes the noise?

Are you asking about the buzz or the whine, or something else? Here is a CFM56 to compare to.

I'm talking about the whine. On reaching full throttle, the two engines sound somewhat similar.

The whining noise is generated by the rotating components in the engine. At takeoff power for an engine of that size, the fan is rotating at about 5200 rpm. This is about 86 times per second. There are also 22 blades on the fan at the front of the engine. This means a given point sees a fan blade pass about 1900 times per second. Each fan blade changes the pressure as it passes, resulting in a tone of about 2kHz. This is the whine that you hear. At takeoff the tips of the fan blades are going supersonic, each one creating a shockwave.

Unfortunately I am unable to watch your video at the moment so I can't say for sure that this is the noise you are hearing, but you have commented that the noise is a whine and not engine buzz. The A320 series is known for having a distinct whine, essentially caused by the pressure equalisation vents for the fuel tanks, which are open to the external airflow.
As Lufthansa describe here, the effect is the same as when you blow over the mouth of a bottle. Lufthansa are retrofitting vortex generators  on their A320s in order to reduce this whine.
Some more interesting reading on this issue is here and here.

I've asked an extremely similar question here, and I'm pretty sure  the OP was NOT talking about these vents. The sound I recognize from the two linked videos is tightly linked to the engine rotation, and doesn't vary much with airspeed.

All high bypass jet engines make this roaring noise due to the blade tips of the first N1 stage (The first fan blades you can see from your seat). At take off this noise is generated by the blades tips which are rotating at 75-95% of maximum power, nearing or exceeding the speed of sound. This creates a MILD continuous sonic shock waves (supersonic bang) sounding like a motorbike. The loudness of the bang depends on the size. A fighter jet aircraft which has a much bigger airframe than that of a fan blade would sound like a small bomb explosion. Technology can reduce the loudness of the roaring but not eliminate it. I've got three videos of Pratt & Witney, IAE and CFM engines on take off but can't attach them here (Don't know how to). They have different high pitch whistling but the same roaring.

Point to this one, as the other answers talk about "whine", and the most prominent sound in the example video is definitely not a whine, but more like an air compressor running at high rpm, matching well with the described source in this answer.